Comment 2 for bug 1801533

Same problem: it does not matter if upgraded from 18.04 or installed new with 18.10. lightdm might not allways be capable initializing graphics leeding to some loop together with systemd turning on backlight, turning it off again, then restarting.

Backlight is turned on, then off about twice a second. After some time backlight electronics break down, killing the monitor.